The Blues added just 24 runs for the loss of their last six wickets on the final morning at the WACA to be all out for 126 and a paltry lead of just eight runs.
They lost 6-3 off the final 52 deliveries with offspinner Marcus North taking 3-9 as he bowled into the footmarks.
WA made hard work of the miniscule run chase, losing Cameron Bancroft stumped second ball to Manjot Singh and Marcus Harris (2) caught at slip attempting a wild slog.
But North (4) and Adam Voges (4) brought up the winning runs, setting WA up for a tilt at the Shield final with games away to go against Queensland and NSW.
The Blues were on top of the ladder going into the match following a thumping innings and 48-run win over Victoria last week at the SCG and remain well in the hunt.
The game was evenly poised after two days with WA 5-263 in reply to NSW’s 344 but, from that point, the Warriors dominated, making 462 in their first innings for a 118-run lead as Voges scored 155 and Sam Whiteman 88.
NSW were then in trouble at stumps on day three at 4-102 but would have still been confident of at least having something to bowl at with first-innings centurion Ryan Carters at the crease.
Carters top-scored for NSW in the second dig with 37 but Sean Abbott, Singh and Josh Hazlewood all failed to score while Trent Copeland was the final wicket to fall for one.
Jason Behrendorff backed up his career-best 5-65 in the first innings for WA with 4-35 in the second while Michael Hogan also claimed 2-17.
In Hobart, Tasmania were daring to dream of a second straight miracle run to the Sheffield Shield final and an unlikely defence of their title.
The Shield champions crushed Queensland by 183 runs at Bellerive to keep their slim final chances alive.
The Ricky Ponting-inspired Tigers came from fourth last season to snatch hosting rights and famously went on to deliver the former Test skipper his first Shield success.
“We were in a very similar place to this last year,” coach Dan Marsh said. “It’s virtually the same situation, so while there’s life there’s hope.”
Tasmania’s second outright win of the season, and first since November, takes them to 16 points on the table, and a mathematical chance of making next month’s final with two matches to play.
Queensland, their opponents in 2012-13 the decider, find themselves in an identical position.
A second batting collapse for the match from the Bulls meant they were never a hope of chasing down the 333 they needed for victory.
Resuming at 1-11 Queensland were 7-53 early on day four before they were all out for 149.
Tasmanian left-arm paceman Sam Rainbird continues to impress and added 4-40 to the three wickets he grabbed in the first innings.
The 21-year-old has stepped up in James Faulkner’s absence and is now his side’s leading wicket-taker with 26 at 24.65 in a breakthrough season.
But Marsh credited Ben Hilfenhaus’s first innings hat-trick as the pivotal moment in the match after his side had put 350 on the board in the first innings. “From that point on we really controlled the game,” he said.
Queensland coach Stuart Law conceded his side struggled on the slow wicket. “After day one the batsmen really struggled to get any momentum going anywhere,” he said. “It probably wasn’t really a fair contest between bat and ball.”
Both sides will need victory in the day/night, pink ball experimental round beginning on March 3.
Tasmania are holding out some hope paceman Jackson Bird could return home from South Africa if not required for the third Test.
The Bulls should get Usman Khawaja (hamstring) back but allrounder Ben Cutting is in doubt with a suspected grade one hamstring tear and did not bowl in the second innings in Hobart.
In Adelaide, Victoria’s middle order batsmen stubbornly resisted South Australia on Sunday to force a draw.
The Bushrangers lost just five wickets on the final day, finishing at 7-334 in their second innings – a lead of 132 runs.
The Redbacks banked innings points to move to 26 points on the Shield table – the same amount as Western Australia, who are top courtesy of a superior quotient.
SA made 6(dec)-511, bowled out Victoria for 309 in their first innings and then enforced the follow-on.
And the Redbacks started Sunday with hopes of forcing an outright win as the Bushrangers resumed their second dig on 2-93.
But the home side were defied by stoic knocks by Cameron White (65), Marcus Stoinis (52), David Hussey (45), Matthew Wade (71 not out) and John Hastings (47).
White, Stoinis and Glenn Maxwell (four) were dismissed before lunch but the Redbacks could only manufacture two more wickets in the day.
After Hussey was run out, Wade and Hastings put on an 83-run stand for the seventh wicket, crucially eating up 29 overs, to help prevent the Victorians losing a fifth consecutive Shield game.
SA’s cause was hampered by a back injury to Joe Mennie which forced the paceman from the field before lunch.
Mennie had claimed the wickets of White and Stoinis and had figures of 3-18 from 9.4 overs when forced off.